[55.03] An Analysis of Longterm AAVSO Observations of the Recurrent Nova RS Ophiuchi

B.Oppenheimer, J.A.Mattei (AAVSO)

RS Ophiuchi is a recurrent nova consisting of an M2 red giant and a blue
companion star. It has undergone five known outbursts, in 1898, 1933, 1958,
1967, and 1985, reaching maximum brightness between 5th and 6th magnitude
within a day. It shows significant light variability between outbursts,
oscillating between visual magnitudes 9.6 and 13.5. Using the photographic
data from Harvard plates from 1890 to 1917 and AAVSO visual data from 1920
to mid-1993, we studied the light behavior of each of the outbursts and
searched for periodic brightness variations between outbursts. The shape
and the decline rates of the outbursts are strikingly similar to each other.
We note here the possibility of an additional unreported outburst in 1945
and support this by the similarity of its decline after 70 days to that of
other outbursts. We analyzed the intervals between outbursts using
date-compensated discrete Fourier transforms (Ferraz-Mello 1981). We find
that while each well observed interval from 1933 to mid-1993 shows strong
periodicity within itself, there is no principal period that is common to
all and the strongest periods range between 941 and 2283 days.

We gratefully acknowledge the support of NASA under grant NAGW-3228 and
the AAVSO Margaret Mayall Assistantship which partially funded this project.